Using wave theory explain how making sound with a wind instrument is essentially the same as making sound with a string instrument.

3Sound Waves

Sound waves are caused by vibrations, and carry energy through a medium.

The speed of sound in a particular medium depends on how well the particles can transmit the compressions and rarefactions of sound waves.

compressionrarefaction 4Properties of Sound Waves

Loudness is determined by intensity.

Intensity depends on the amplitude of the sound wave as well as your distance from the source of the waves.

The greater the intensity of a sound, the louder the sound will seem.

5Sound Intensity and Decibels 6Properties of Sound (continued)

Pitch is determined by frequency.

The pitch is a measure of how high or low a sound is perceived to be depending on the frequency of the sound wave.

A high-pitched sound corresponds to a high-frequency, and a low-pitched sound corresponds to a low frequency.

7The Doppler Effect

Frequency changes when the source of waves is moving.

The Doppler effect is an observed change in the frequency of a wave when the source or observer is moving. Doppler

8Properties of Sound (continued)

Humans hear sound waves in a limited frequency range.

Any sound with a frequency below the range of human hearing is known as an infrasound.

An infrasound is slow vibrations of frequencies lower than 20 Hz.

Any sound with a frequency above human hearing range is known as an ultrasound.

An ultrasound is any sound wave with frequencies higher than 20 000 Hz. audible sound

9Standing Waves

Musical instruments rely on standing waves.

Standing waves can exist only at certain wavelengths on a string.

The primary standing wave on a vibrating string has a wavelength that is twice the length of the string.

The frequency of this wave is called the fundamental frequency. frequency

10Harmonics and Resonance

Harmonics give every instrument a unique sound.

Certain whole-number multiples of the fundamental frequency are called harmonics.

Every musical instrument has a characteristic sound quality resulting from the mixture of harmonics.

Instruments use resonance to amplify sound.

Resonance is a phenomenon that occurs when two objects naturally vibrate at the same frequency. resonance

11Application of Resonance

Sound is not the only type of wave that experiences resonance.

In November of 1940, the original Tacoma Narrows Bridge collapsed due to its structure at the midspan resonating with 42mph wind.

You Tube video of Narrows bridge collapse

12Ultrasound and Sonar

Ultrasound imaging is used in medicine.

The echoes of very high frequency ultrasound waves, between 1 million and 15 million Hz, are used to produce computerized images called sonograms.

Some ultrasound waves are reflected at boundaries.

Some sound waves are reflected when they pass from one type of material into another.

How much sound is reflected depends on the density of the materials at each boundary.

13Ultrasound and Sonar (continued)

Sonar, sound navigation and ranging, is a system that uses acoustic signals and echo returns to determine the location of objects or to communicate.

Sonar is used for underwater location.

A sonar system determines distance by measuring the time it takes for sound waves to be reflected back from a surface. sonar

d vt

d is distance

v is the average speed of the sound waves in water

t is time

14Speed of Sound

Were going to do a little experiment or two together to see if we can calculate the speed of sound. Listen carefully to the instructions.

You will need the lab worksheet and materials.

When you are not working on one of the lab activities, you should be working on this assignment

p. 498 review 1-7, 9, 10 answer in complete sentences.

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